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Deno Fetch Event Adapter

Dispatches global fetch events using Deno's native HTTP server.

It is mostly intended as a temporary solution until Deno implements the Service Worker spec directly.
This has been scrapped, but this module works just fine for local testing, developing Cloudflare Workers while offline, and similar use cases.


// file: "worker.js"
import '';

// This module adds a global `FetchEvent`
if (typeof FetchEvent !== 'undefined') console.log(true);

// This module also adds global type declarations, s.t. this type-checks:
self.addEventListener('fetch', event => {
  const ip = event.request.headers.get('x-forwarded-for');
  event.respondWith(new Response(`Hello ${ip ?? 'World'}`));

Your script needs the --allow-net permissions. It also requires a --location, to know on which port to listen for incoming connections:

deno run --allow-net --location=http://localhost:8000 worker.js

If you set the --location to either HTTPS or port 443, you have to provide a --cert and a --key parameter. Your script will also need the read permission to read the files:

deno run --allow-net --allow-read --location=https://localhost:8000 worker.js \
  --cert=./path/to/cert.pem \

Error Handling

If an error occurs during estabslishing a connection (e.g. invalid certificate, etc...), the error is dispatched as a global error event rather then crashing the process. You can add custom logging like this:

self.addEventListener('error', event => {

This module is part of the Worker Tools collection

Worker Tools are a collection of TypeScript libraries for writing web servers in Worker Runtimes such as Cloudflare Workers, Deno Deploy and Service Workers in the browser.

If you liked this module, you might also like:

  • 🧭 Worker Router --- Complete routing solution that works across CF Workers, Deno and Service Workers
  • 🔋 Worker Middleware --- A suite of standalone HTTP server-side middleware with TypeScript support
  • 📄 Worker HTML --- HTML templating and streaming response library
  • 📦 Storage Area --- Key-value store abstraction across Cloudflare KV, Deno and browsers.
  • 🆗 Response Creators --- Factory functions for responses with pre-filled status and status text
  • 🎏 Stream Response --- Use async generators to build streaming responses for SSE, etc...
  • 🥏 JSON Fetch --- Drop-in replacements for Fetch API classes with first class support for JSON.
  • 🦑 JSON Stream --- Streaming JSON parser/stingifier with first class support for web streams.

Worker Tools also includes a number of polyfills that help bridge the gap between Worker Runtimes:

Fore more visit